Effects Of Surface Acoustic Waves Research Articles

Effects of surface acoustic waves on reversal of magnetic domains in patterned films with perpendicular magnetic anisotropy

In this work, the magnetization reversal of patterned Pt/Co/Pt multilayers influenced by surface acoustic waves is investigated. For each patterned cell, the magnetization reversal involves formation of a reversal nucleus followed by rapid motion of a domain wall. The nucleation probability of the reversal nucleus increases with the power of the applied surface acoustic wave, which is explained by the magnetic droplet model, and fitting the experimental results with this model gives important parameters such as the domain-wall energy density and the reduction rate of local perpendicular anisotropy. The fitting results for different patterned cells are consistent with the experimental results, which validates this model for dealing with such issues.

Effects of surface acoustic waves on droplet impact dynamics

HypothesisSurface acoustic waves (SAW) propagating along a solid surface can significantly affect the dynamics of droplet impact. Although droplet impact in presence of SAW has been attempted recently, here, we investigate the effects of surface wettability, droplet size, impact velocity, and SAW power on the impact and spreading dynamics along with post-impact oscillation dynamics of a drop. ExperimentsHere, we study droplet impact on a surface exposed to traveling SAW produced using an interdigitated electrode patterned on a piezoelectric substrate. The effects of Weber number (We), surface wettability, and SAW power on the impact and spreading dynamics and post-impact oscillation dynamics are studied. FindingsOur study unravels that the interplay between capillary and viscous forces, and inertia forces arising due to pre-impact kinetic energy and SAW-induced bulk acoustic streaming underpins the phenomena. Remarkably, we find that the effect of SAW on droplet impact dynamics is predominant in the case of a hydrophilic (HPL) substrate at a higher SAW power and smaller We and hydrophobic (HPB) substrate irrespective of SAW power. Our study reveals that the maximum droplet spreading diameter increases with SAW power at smaller We for an HPL surface whereas it is independent of SAW power at higher We. Post-impact oscillation of a droplet over an HPL surface is found to be overdamped with a smaller amplitude compared to an HPB substrate, and a faster decay in oscillation amplitude is observed in the case of an HPB surface and higher We. Our study provides an improved understanding of droplet impact on a surface exposed to SAW that may find relevance in various practical applications.

Silicon-photonics acoustic detector for optoacoustic micro-tomography

Medical ultrasound and optoacoustic (photoacoustic) imaging commonly rely on the concepts of beam-forming and tomography for image formation, enabled by piezoelectric array transducers whose element size is comparable to the desired resolution. However, the tomographic measurement of acoustic signals becomes increasingly impractical for resolutions beyond 100 µm due to the reduced efficiency of piezoelectric elements upon miniaturization. For higher resolutions, a microscopy approach is preferred, in which a single focused ultrasound transducer images the object point-by-point, but the bulky apparatus and long acquisition time of this approach limit clinical applications. In this work, we demonstrate a miniaturized acoustic detector capable of tomographic imaging with spread functions whose width is below 20 µm. The detector is based on an optical resonator fabricated in a silicon-photonics platform coated by a sensitivity-enhancing elastomer, which also effectively eliminates the parasitic effect of surface acoustic waves. The detector is demonstrated in vivo in high-resolution optoacoustic tomography.

Key influence factors on suspension compressible fluid through pore induced by SAW (motion of black powder in pipeline)

The flow of compressible fluid with suspended particles in circular tube under the effect of surface acoustic wave (SAW) is investigated. The system of differential equations for both the fluid and particles phases is solved using the perturbation method to simplify the system of equations. The time average of flow rate is calculated, and the effect of Reynolds number, wave number, concentration and density ratio is studied. Comparison between our study and the previous is discussed. The effect of SAW on the flow of suspended natural gas is taken as an application. Real data are used to introduce this application. The SAW on pipeline may avoid accumulation of black powder.

Computational approach reveals mechanisms behind material modification through surface acoustic waves

Model based on atomistic molecular dynamics describes unexplored nonlinear effects of surface acoustic waves and examines processes underlying acoustically induced surface modification.

Dissociation and synthesis of target components during laser ablation of LiNbO3

This paper shows the results of thermodynamic analysis of interfacial interaction in the lithium-niobium-oxygen system. The temperature dependences of the change in the Gibbs free energy calculated, taking into account the non-linear temperature dependences of the thermophysical properties of materials. Additionally, estimated the possibility of dissociation reactions of lithium and niobium oxides, as well as the reactions of lithium and niobium with oxygen. The results obtained can be used in the design and manufacture of integrated acousto-optic and piezoelectric devices, as well as for sensitive elements of sensors using various effects of surface acoustic waves.

Formation of SiO2 buffer layer for LiNbO3 thin films growth

This paper shows the results of study of the effect of SiO2 buffer layer thickness on the morphological parameters of nanocrystalline LiNbO3 films formed by pulsed laser deposition. It has been established that with increasing in the thickness of SiO2 buffer layer from 10 nm to 50 nm, the roughness of LiNbO3 films decreases from 5.1 nm to 4.4 nm. The minimum value of the grain diameter (118 nm) corresponds to the thickness of the buffer layer equal to 50 nm. The results obtained can be used in the design and manufacture of integrated acousto-optic and piezoelectric devices, as well as sensitive elements of sensors using various effects of surface acoustic waves.

Acoustic enhancement of surface reactions

Abstract

Acoustically modulated optical emission of hexagonal boron nitride layers

We investigate the effect of surface acoustic waves on the atomic-like optical emission from defect centers in hexagonal boron nitride layers deposited on the surface of a LiNbO3 substrate. The dynamic strain field of the surface acoustic waves modulates the emission lines resulting in intensity variations as large as 50% and oscillations of the emission energy with an amplitude of almost 1 meV. From a systematic study of the dependence of the modulation on the acoustic wave power, we determine a hydrostatic deformation potential of about 40 meV/% for defect centers in this two-dimensional material. Furthermore, we show that the dynamic piezoelectric field of the acoustic wave could contribute to the stabilization of the optical properties of these emission centers. Our results show that surface acoustic waves are a powerful tool to modulate and control the electronic states of two-dimensional materials.

Enhancement of plant leaf transpiration with effective use of surface acoustic waves: effect of wave frequency.

Water transport in vascular plants provides remarkable opportunities for various engineering applications due to its highly efficient and powerless transportability. Several previous studies were conducted to regulate the biological responses of plants using noninvasive audible or ultrasound waves. However, the control mechanism of acoustic stimuli applied to plants has not been investigated yet. Thus, the practical application of these stimuli to real plants still exhibits technological limitations. This study experimentally investigated the effects of surface acoustic wave (SAW) frequency on plant transpiration to understand the acoustic-activated leaf transpiration and utilize the advantages of SAW. We captured consecutive images of the enhanced water transport in the test plant (Epipremnum aureum) by SAW at three different frequencies (10, 15, and 20 MHz). The dye solution at 15 MHz SAW presented the highest intensity value after 40 min of SAW stimulation. The excitation areas for 15 and 20 MHz SAWs were decreased to 42.3% and 22.6%, respectively, compared with that of 10 MHz SAW. The transpiration rates were directly measured to compare water transport enhancement quantitatively when different SAW frequencies were applied to the same plant leaves. The water transport in the leaves was maximized at 15 MHz SAW, regardless of excitation area.

The Effect of Surface Acoustic Waves on Bacterial Load and Preventing Catheter- associated Urinary Tract Infections (CAUTI) in Long Term Indwelling Catheters

The authors evaluate a novel Surface Acoustic Wave Actuator and its effect on preventing CAUTI. This is a double blinded randomized control trial, of the Uroshield™ device. 55 patients in a skilled nursing facility chain being treated with long term indwelling catheters were evaluated. There was a significant difference between the treated group and the placebo group in the number of Colony Forming Units present upon evaluation, as well as on the number of treated UTI’s. The effect lasted beyond the time of active treatment.

Control of single photon emitters in semiconductor nanowires by surface acoustic waves

We report on an experimental study into the effects of surface acoustic waves on the optical emission of dot-in-a-nanowire heterostructures in III-V material systems. Under direct optical excitation, the excitonic energy levels in III-nitride dot-in-a-nanowire heterostructures oscillate at the acoustic frequency, producing a characteristic splitting of the emission lines in the time-integrated photoluminescence spectra. This acoustically induced periodic tuning of the excitonic transition energies is combined with spectral detection filtering and employed as a tool to regulate the temporal output of anti-bunched photons emitted from these nanowire quantum dots. In addition, the acoustic transport of electrons and holes along a III-arsenide nanowire injects the electric charges into an ensemble of quantum dot-like recombination centers that are spatially separated from the optical excitation area. The acoustic population and depopulation mechanism determines the number of carrier recombination events taking place simultaneously in the ensemble, thus allowing control of the anti-bunching degree of the emitted photons. The results presented are relevant for the dynamic control of single photon emission in III-V semiconductor heterostructures.

Metamaterial based on elastic mechanics

In recent years, artificial metamaterials base on micro structures are showing huge development potential in fields of materials science, acoustics, seismology and information technologies, due to their devisable physical singularities which do not exist in natural materials. The study of metamaterial was born out of electromagnetic metamaterial. Nowadays, metamaterials have achieved a big leap forward with developments in the fields of acoustic, thermal, static, static magnetic and elastic mechanics, which greatly expand their study fields. With the help of a Milton graph, we focus on the extraordinary characteristics of novel elastic mechanics-based metamaterials and their species, such as acoustic metamaterials with negative mass density and elastic modulus, auxetic metamaterials with negative Poissons ratio, inverse bulging metamaterials with shear modulus G =0 and ultra-light materials with high strength. In addition, combining with the transform mechanical, this paper focuses on the propagation characteristics of acoustic and elastic waves in this elastic mechanics metamaterial and then elaborated the characteristics and physical effects of surface acoustic waves in the interface of metamaterials with negative elasticity parameters. Finally, we make a summary and prospect of the development of metamaterials combining with the elastic mechanics metamaterial research condition in China, such as metamaterial and acoustic metamaterial operating acoustic and elastic wave propagation using the elastic mechanics, design and development of a new type of elastic mechanics metamaterial. We hope this will help to accelerate the application of this metamaterial in many research fields.

Analysis and Impact of Surface Acoustic Wave Filter in-Band Ripple on Testing and Measurement of High Data Rate Communications

In this paper, we present a background and theory of the effect of Surface Acoustic Wave (SAW) Filter Module (SFM) in-band ripple on high data rate communications parameters such as the Error Vector Magnitude (EVM). In addition, we present analyses and statements for the choice of unbalanced S-parameters set of the SFM over balanced S-parameters set of the SFM in measurements and Agilent’s Advance Design System (ADS) Ptolemy simulations. A test and measurement setup using Agilent’s equipment will be presented.

Surface Acoustic Waves Enhance Neutrophil Killing of Bacteria

Biofilms are structured communities of bacteria that play a major role in the pathogenicity of bacteria and are the leading cause of antibiotic resistant bacterial infections on indwelling catheters and medical prosthetic devices. Failure to resolve these biofilm infections may necessitate the surgical removal of the prosthetic device which can be debilitating and costly. Recent studies have shown that application of surface acoustic waves to catheter surfaces can reduce the incidence of infections by a mechanism that has not yet been clarified. We report here the effects of surface acoustic waves (SAW) on the capacity of human neutrophils to eradicate S. epidermidis bacteria in a planktonic state and within biofilms. Utilizing a novel fibrin gel system that mimics a tissue-like environment, we show that SAW, at an intensity of 0.3 mW/cm2, significantly enhances human neutrophil killing of S. epidermidis in a planktonic state and within biofilms by enhancing human neutrophil chemotaxis in response to chemoattractants. In addition, we show that the integrin CD18 plays a significant role in the killing enhancement observed in applying SAW. We propose from out data that this integrin may serve as mechanoreceptor for surface acoustic waves enhancing neutrophil chemotaxis and killing of bacteria.

Coupling liquids acoustic velocity effects on elastic metallic bioglass properties

The effect of surface acoustic wave, SAW, velocities of coupling liquids on acoustical properties of several bulk metallic glasses, BMG, has been investigated using simulation program based on acoustic microscopy. Thus, we determined variations of critical angles at which the excitation of longitudinal mode, θL and Rayleigh mode, θR occurs as a function of wave velocities in different coupling liquids, Vliq. Linear relations of the form θi=ai0+βiVliq were deduced. The importance of such formula, used with Snell’s law, lies in the direct determination of SAW velocities and consequently mechanical properties of BMGs.

Effect of surface acoustic waves on the viability, proliferation and differentiation of primary osteoblast-like cells.

Surface acoustic waves (SAWs) have been used as a rapid and efficient technique for driving microparticles into a three-dimensional scaffold matrix, raising the possibility that SAW may be effective in seeding live cells into scaffolds, that is, if the cells were able to survive the infusion process. Primary osteoblast-like cells were used to specifically address this issue: To investigate the effects of SAW on the cells' viability, proliferation, and differentiation. Fluorescence-labeled osteoblast-like cells were seeded into polycaprolactone scaffolds using the SAW method with a static method as a control. The cell distribution in the scaffold was assessed through image analysis. The cells were far more uniformly driven into the scaffold with the SAW method compared to the control, and the seeding process with SAW was also significantly faster: Cells were delivered into the scaffold in seconds compared to the hour-long process of static seeding. Over 80% of the osteoblast-like cells were found to be viable after being treated with SAW at 20 MHz for 10-30 s with an applied power of 380 mW over a wide range of cell suspension volumes (10-100 mul) and cell densities (1000-8000 cellsmul). After determining the optimal cell seeding parameters, we further found that the treated cells offered the same functionality as untreated cells. Taken together, these results show that the SAW method has significant potential as a practical scaffold cell seeding method for tissue and orthopedic engineering.

Numerical simulation of the ultrasonic waves generated by ring-shaped laser illumination patterns

The generation of ultrasound in aluminum plate subjected to ring-shaped laser beam illumination has been studied quantitatively by using the finite element method. The superposition effects of surface acoustic waves on the top surface and the bulk ultrasonic waves on the rear surface of specimen have been obtained in a single simulation. The typical displacement profiles of the bulk ultrasonic wave at various depths along the central axis of the ring are obtained for three different radii, and the effect of the ring radius on the focal depths of the compression and shear mode are determined. The numerical results confirm that the focal depth of a bulk acoustic mode is determined by the directivity patterns of the acoustic mode generated by point-like laser sources via a thermoelastic mechanism, which depends on the physical constants of elastic medium.

PEEM study of work function changes in Cu, Au and Pd metal surfaces with surface acoustic wave propagation

The effects of surface acoustic wave (SAW) on the work function of Cu, Au and Pd metal surfaces with different surface structures were studied by photoelectron emission microscopy (PEEM). SAW propagation produced bright PEEM images for Cu, Au and Pd metal surfaces consisting of high-index planes and step sites, whereas it yielded dark images for the metals exposing low-index planes, indicating that the SAW enhanced photoemission from rough metal surfaces containing coordinatively-unsaturated metal atoms and lowered that from densely packed smooth metal surfaces. Changes in the PEEM images with SAW-on and SAW-off were reversible and were associated with decreases and increases in the work function of the metal surfaces, respectively. The SAW caused periodic and vertical lattice displacement, and it was demonstrated that large lattice displacement was responsible for work function changes from coincidence between the patterns of photoemission and lattice displacement. A mechanism for work function changes is proposed on the basis of effects on the spatial structures and electronic properties of metal surfaces.

Theoretical analysis of damping effects of guided elastic waves at solid∕fluid interfaces

A theoretical description of ideal and viscous fluid media is proposed to address the problem of modeling damping effects of surface acoustic waves and more generally of any guided elastic waves at the interface between viscous fluids and solids. It is based on the Fahmy-Adler eigenvalue representation of the elastic propagation problem, adapted to provide Green’s function of the considered media. It takes advantage of previous efforts developed to numerically stabilize Green’s-function computation process. This function is used to compute a harmonic admittance according to the Blötekjaër approach. The influence of acoustic radiation and viscosity effects on different kinds of waves excited on various substrates is reported and discussed.